Issue 48

K. Kimakh et alii, Frattura ed Integrità Strutturale, 48 (2019) 429-441; DOI: 10.3221/IGF-ESIS.48.41 431 Table 2 : The mechanical properties of AISI 1045 steel. Specimens and surface preparation The geometric characteristics of the specimens considered for fatigue tests were established according to the standard ASTM E466-7 (fatigue test for metallic materials) in Fig. 1 [13]. Figure 1 : Geometric characteristic of the fatigue specimen (ASTM E466-7). The fatigue test specimens were machined to obtain four batches with different surface state between 3µm and 0.5µm of roughness. In order to determine the cutting conditions expected to generate specimens with a controlled surface roughness, a mathematical model that expresses the roughness function of cutting conditions was adopted [14]. Tab. 3 summarizes the cutting parameters (spindle speed N, feed rate f, depth of cut ap and tool nose radius r ɛ ) used for the different batches (L1, L2, L3 and L4). The turning operations were carried out on a CNC lath Alpha 1530XS. Then the specimens were controlled. For the surface state, the roughness were measured using the surface roughness tester of "Mitutoyo" SJ-201M conforming to the standard EN ISO 4288 [15]. For each batch Li, the arithmetical mean height Ra and the maximum height of the profile Ry values were recorded. The results obtained were presented in Tab. 4. Batches Rough Finishing N (rpm) f (mm/rev) ap(mm) r ɛ (mm) N (rpm) f (mm/rev) ap (mm) r ɛ (mm) L1 1200 0.15 0.5 0.8 2500 0.25 0.5 0.8 L2 1200 0.15 0.5 0.8 2500 0.15 0.5 0.8 L3 1200 0.15 0.5 0.8 2500 0.05 0.3 0.8 L4 1200 0.15 0.5 0.8 1200 0.04 0.6 0.4 Table 3 : Cutting conditions for fatigue specimen machining. Material Mechanical properties AISI 1045 S y02 [MPa] S UTS [MPa] A% E [ GPa] HV 432 650 23 210 185